ИСТИНА

This work was devoted to a comparative study of inhibitive effect of ouabain and marinobufagenin on Na,K-ATPase and the binding of this CTS to the enzyme. According to our ITC data affinity of MBG shows week dependence on the NKA state (E2P or E1), while the ouabain affinity to NKA dramatically decreases in E1 state (Table 1). However the inhibition constants of NKA hydrolytic activity by MBG and ouabain are similar. Molecular modeling results show that ouabain and MBG binding result in different positioning of the NKA transmembrane segments forming the binding site (Fig. 5 F), which consequently causes a range of structural changes in the cytosolic part of the molecule. These changes may be conveyed to the cytosolic part of the molecule mainly via interaction of CTS with the most extended transmembrane segment αМ5 reaching the nucleotide binding domain.